Asymmetric cochlear implant electrodes and method

Abstract

An implantable lead may include an insulating substrate and a first asymmetric electrode formed on the insulating substrate. The first asymmetric electrode may have external perimeter edges defining a boundary between an exposed portion of the first electrode and the insulating substrate, wherein the external perimeter edges of the first electrode have asymmetric edge lengths.

What is claimed is: 
     
       1. An implantable cochlear lead comprising:
 an insulating carrier adapted for placement in a cochlea; and 
 first and second stimulation electrodes, each electrode carried by the insulating carrier and bounded by external perimeter edges comprising a jagged edge having an edge length and a smooth edge opposite the jagged edge and having an edge length shorter than the edge length of the jagged edge; 
 wherein the jagged edge of the second electrode is disposed facing the jagged edge of the first electrode, and the smooth edge of the second electrode is disposed away from the smooth edge of the first electrode. 
 
     
     
       2. The lead of  claim 1 , wherein the first and second stimulation electrodes are located on an apical tip of the lead such that the jagged edge of the first electrode is distal of the smooth edge of the first electrode and the jagged edge of the second electrode is distal of the smooth edge of the second electrode. 
     
     
       3. The lead of  claim 1 , further comprising:
 third and fourth stimulation electrodes, each electrode carried by the insulating carrier and bounded by external perimeter edges comprising a jagged edge and a smooth edge; 
 wherein the smooth edge of the third electrode is disposed adjacent the smooth edge of the second electrode, the jagged edge of the fourth electrode is disposed adjacent the jagged edge of the third electrode, and the smooth edge of the fourth electrode is disposed away from the smooth edge of the third electrode. 
 
     
     
       4. The lead of  claim 1 , wherein the first stimulation electrode has an overall shape that is rectangular or round. 
     
     
       5. The lead of  claim 1 , wherein the first stimulation electrode is a ring. 
     
     
       6. The lead of  claim 1 , wherein the jagged edges are toothed, slotted, castellated, or scalloped. 
     
     
       7. The lead of  claim 6 , wherein the jagged edges have regular teeth, slots, castellations, or scallops. 
     
     
       8. The lead of  claim 1 , wherein the insulating carrier comprises a thermoformed substrate. 
     
     
       9. The lead of  claim 8 , further comprising a pocket of flexible polymer formed in the substrate between the first and second electrodes, wherein the flexible polymer has a greater flexibility than the substrate. 
     
     
       10. The lead of  claim 1 , further comprising a protrusion between the jagged edges, the protrusion configured to direct an electrical field into target tissue. 
     
     
       11. A method for stimulating target tissue comprising:
 implanting the lead of  claim 1  in a cochlea; and 
 applying a voltage across the first and second stimulation electrodes to stimulate the target tissue. 
 
     
     
       12. A method for stimulating target tissue comprising:
 implanting the lead of  claim 1  in a cochlea; 
 electrically coupling the first stimulation electrode to the second stimulation electrode to form a split electrode; and 
 applying a voltage across the split electrode and one or more other electrodes that are not adjacent the first or second stimulation electrodes to stimulate the target tissue. 
 
     
     
       13. An implantable cochlear lead comprising:
 an insulating carrier adapted for placement in a cochlea; 
 a first stimulation electrode carried by the insulating carrier and bounded by external perimeter edges comprising:
 a jagged edge having an edge length, and 
 a smooth edge opposite the jagged edge and having an edge length shorter than the edge length of the jagged edge; and 
 
 a second stimulation electrode carried by the insulating carrier and bounded by external perimeter edges comprising:
 a jagged edge having an edge length, and 
 a smooth edge opposite the jagged edge and having an edge length shorter than the edge length of the jagged edge; 
 
 wherein the first and second electrodes are disposed on a distal tip of the lead with their jagged edges facing each other and distal of their smooth edges. 
 
     
     
       14. The lead of  claim 13 , wherein the first stimulation electrode has an overall shape that is rectangular. 
     
     
       15. The lead of  claim 13 , wherein the first stimulation electrode has an overall shape that is round. 
     
     
       16. The lead of  claim 13 , wherein the jagged edges are toothed, slotted, castellated, or scalloped. 
     
     
       17. The lead of  claim 16 , wherein the jagged edges are serpentine or have rounded peaks. 
     
     
       18. The lead of  claim 16 , wherein the jagged edges have regular teeth, slots, castellations, or scallops. 
     
     
       19. A method for stimulating target tissue comprising:
 implanting the lead of  claim 13  in a cochlea; and 
 applying a voltage across the first and second stimulation electrodes to stimulate the target tissue. 
 
     
     
       20. A method for stimulating target tissue comprising:
 implanting the lead of  claim 13  in a cochlea; 
 electrically coupling the first stimulation electrode to the second stimulation electrode to form a split electrode; and 
 applying a voltage across the split electrode and one or more other electrodes that are not adjacent the first or second stimulation electrodes to stimulate the target tissue.